Five- and Six-Bar Running Board Linkages With Kinematic Lock
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Solution Overview
Problem
Current automated running board mechanisms using four bar linkages lack a reliable kinematic lock in the deployed position, allowing back driving, and rely on unreliable worm gear pairs to prevent it, which constrains the use of efficient drive units.
Innovation Solution
The development of five and six bar linkage designs with integrated self-locking mechanisms, including roller joints and traditional pivot joints, that prevent back driving in both deployed and stowed positions, enabling the use of high-efficiency drive units by ensuring the running boards do not over deploy or stow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four bar linkages are used to deploy and stow the running board, then the mechanism is simple, but back driving is possible and kinematic lock is unreliable
Solution Approach 1:
The four bar linkage is segmented into a five bar or six bar linkage by adding an additional link and pivot point. This segmentation creates a distinct lock position where the linkage geometry prevents back driving, while maintaining relative structural simplicity through the use of standard pivot joints and conventional mechanical elements.
2Reliability
If worm gear pairs are used to prevent back driving, then back driving is prevented, but drive unit efficiency is reduced and design flexibility is constrained
Solution Approach 1:
The worm gear mechanical system is replaced with a pure kinematic lock mechanism based on linkage geometry. The five bar and six bar linkages create a lock position through their geometric configuration, eliminating the need for worm gears and their associated friction losses, thereby maintaining high drive unit efficiency while preventing back driving.
3Reliability
If five or six bar linkages with kinematic lock are used, then back driving is prevented and drive unit efficiency is improved, but mechanism complexity increases
Solution Approach 1:
The linkage structure parameters are changed from four bars to five or six bars, adding one additional link and pivot point. This parameter change creates the kinematic lock capability while maintaining a relatively simple structure that uses conventional mechanical elements, balancing the increased functionality with acceptable structural complexity.
Data Source
AI summary
All designs have features that prevent the running boards from over deploying and stowing. This ensures the mechanism does not exceed the design range of motion and prevents any excess forces on the system or vehicle. All designs use kinematic locks to prevent back driving in stowed and deployed positions, which allows more efficient gearboxes to be used.